Photochromic compounds based on ring opening and closing of an [1,3]oxazine compound

Abstract

We have designed a molecular switch based on the photoinduced opening and thermal closing of a [1,3]oxazine ring. A substituted [1,3]oxazine compound described as having a general (i.e., unsubstituted) structure with fused indoline and benzooxazine fragments such that they share a common bond in the [1,3]oxazine compound: (i) the bond connecting positions 1 and 2 of the indoline fragment and (ii) the bond connecting positions 2 and 3 of the benzooxazine fragment. Irradiation by light of suitable wavelength and intensity of this photochromic compound induces cleavage of a [C—O] bond of the [1,3]oxazine ring to form a phenolate chromophore. The photogenerated (e.g., colored) isomer may revert thermally to the starting (e.g., colorless) oxazine. Alternatively, the switch may be between isomers of the compound that absorb at different wavelengths. Reversible coloration of silica or polymeric materials and switching optical signals may involve many cycles of interconversion between different colored states. A colorless/colored state may be maintained by constant irradiation or chemical trapping.

1. A method of optically switching a photochromic compound or material incorporating said compound, wherein said compound is a substituted [1,3]oxazine as shown in Formula I 
       
         
           
           
               
               
           
         
         wherein said R 1  is selected from the group consisting of hydrogen, hydroxyl, C1-C4 alkyls, substituted C1-C4 alkyls, C5-C6 cycloalkyls, substituted C5-C6 cycloalkyls, C5-C6 aryls, substituted C5-C6 aryls, C5-C6 heterocycles, and substituted C5-C6 heterocycles; said R 2  is selected from the group consisting of hydrogen, hydroxyl, C1-C4 alkyls, substituted C1-C4 alkyls, C5-C6 cycloalkyls, substituted C5-C6 cycloalkyls, C5-C6 aryls, substituted C5-C6 aryls, C5-C6 heterocycles, and substituted C5-C6 heterocycles; said R 3  is selected from the group consisting of hydrogen, hydroxyl, C1-C4 alkyls, substituted C1-C4 alkyls, C5-C6 cycloalkyls, substituted C5-C6 cycloalkyls, C5-C6 aryls, substituted C5-C6 aryls, C5-C6 heterocycles, and substituted C5-C6 heterocycles; said R 4  is selected from the group consisting of hydrogen, hydroxyl, C1-C4 alkyls, substituted C1-C4 alkyls, C5-C6 cycloalkyls, substituted C5-C6 cycloalkyls, C5-C6 aryls, substituted C5-C6 aryls, C5-C6 heterocycles, and substituted C5-C6 heterocycles; and said R 5  is a nitrogen-containing group or any other electron withdrawing substituent; 
         said method comprising irradiating said compound or material incorporating said compound with light to switch optically from the compound to its phenolate derivative, wherein light induces cleavage of a [C—O] bond in the compound's oxazine ring to produce the phenolate derivative by ring cleavage. 
       
     
     
       2. The method according to  claim 1 , wherein said compound switches to its phenolate derivative in 250 ns or less. 
     
     
       3. The method according to  claim 1 , wherein said switch results in absorbance of visible light to shift from colorless to colored when the compound isomerizes to its phenolate derivative. 
     
     
       4. The method according to  claim 1 , wherein said switch results in the maximum absorbance wavelength to shift between the compound and its phenolate derivative by a difference of at least 50 nm. 
     
     
       5. The method according to  claim 1 , wherein said switch results in the maximum absorbance wavelength to shift between the compound and its phenolate derivative by a difference of at least 200 nm. 
     
     
       6. The method according to  claim 1 , wherein said light has a wavelength from 200 nm to 800 nm. 
     
     
       7. The method according to  claim 1 , wherein said light has a wavelength from 800 nm to 1300 nm. 
     
     
       8. The method according to  claim 1  further comprising not irradiating said phenolate derivative to switch back by thermal re-isomerization. 
     
     
       9. The method according to  claim 1  further comprising trapping said compound in hemiaminal form by using a nucleophile to compete with ring closing. 
     
     
       10. The method according to  claim 1 , wherein isomerization between said compound and its phenolate derivative is possible over greater than 1000 excitation cycles.